Thanks for the query.
Yes, you can use the tablets.
These should be started at-least 5 days before your expected date of periods. So you can start from 25th as you mentioned. And have to continue till the date you want to postpone the periods.
Sometimes you can have nausea
sensation etc side effects.
But usually these will subside soon. If needed you can go for symptomatic treatment.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429